In a theater there are 12 chairs in the first row, each row has 2 more chairs than the previous row, and there are 10 rows. How many chairs are there in the theate

210

Step-by-step explanation:

The first term of the sequence, a1, is 12. The common difference, d, is 2. The number of terms is n = 10. The sum is given by the formula ...

Sn = (2a1 + d (n-1)) (n/2)

Filling in the numbers, this is ...

S10 = (2·12 + 2 (10-1)) (10/2) = (24+18) (5) = 210

There are 210 chairs in the theatre.